#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>

using namespace std;

int main()
{
	int X, Y;
	int sum = 0;
	cin >> X >> Y;
	if (X > Y)
	{
		swap(X, Y);
	}
	for (int i = X + 1; i < Y; i++)
	{
		if (i % 2 != 0)
		{
			sum += i;
		}
	}
	cout << sum;
	return 0;
}